FAYETTEVILLE, Ark. - A team of University of Arkansas researchers recently released a study that will have everyone digging for bones. Digging, planting, weeding and watering, that is.

The researchers have linked regular yard work to the prevention of osteoporosis, finding that women aged 50 and older who gardened at least once a week showed higher bone density readings than those who performed other types of exercise - including jogging, swimming, walking and aerobics.

Research has long shown that weight-bearing exercise can help women maintain healthy bones. But the University of Arkansas study examines which types of weight-bearing exercise have the strongest impact on bone density, said Lori Turner, assistant professor of health sciences and lead researcher on the project.

By knowing which exercises provide the greatest benefit, women can design a workout regimen that will ensure strong bones as they age. Such preventative measures may reduce the number of people who develop osteoporosis - a debilitating disease that currently threatens more than 28 million Americans.

"Within our study, more than half the women - 57 percent - showed low bone density. There’s no question that osteoporosis is a problem in our society," Turner said. "But if we persist only in treating this disease, the number of victims will never drop. We have to find ways to prevent it."

As a registered dietician and as a researcher, Turner has spent the past three years trying to plant that idea in the medical community and in the minds of women, young and old. Presented at the National Alliance for Health, Physical Education, Recreation and Dance conference, this latest study adds another weapon that women can use in the fight against osteoporosis.

To gain a comprehensive look at the effects of exercise on older women, Turner needed a large field of subjects. She found it in the National Health and Nutrition Examination Survey - a dataset collected by the National Center for Health Statistics, which contains information on more than 40,000 people.

Turner first weeded out the youngest subjects, leaving a pool 3,310 women aged 50 and older. She then examined how often these women performed different activities, including yard work, calisthenics, bicycling, dancing, aerobics, swimming, jogging, walking and weight training.

Turner compared each activity to bone mass, finding that bicycling, aerobics, dancing, yard work and weight training were linked to higher levels of mineral density. The researchers then performed a regression model analysis - a statistical assessment that examined each activity independently, ensuring that no two overlapped.

The results showed only two activities to be significant for maintaining healthy bone mass - yard work and weight training.

"We hadn’t expected yard work to be significant," Turner said. "It’s taken for such a dainty activity. But there’s a lot of weight-bearing motion going on in the garden - digging holes, pulling weeds, pushing a mower."

An additional benefit of gardening is the fact that it’s performed outdoors, said Turner. Exposure to sunlight boosts vitamin D production, which aids the body in calcium absorption.

While weight-bearing activity and vitamin D work directly to strengthen women’s bones, yard work provides indirect benefits as well. Of all the activities, yard work proved the most popular, with nearly half of the subjects - 1,384 women - claiming to garden at least once a week. Such popularity makes it a highly effective preventative measure.

In recommending exercise options to older women, health professionals must consider three factors: the activity’s effect on bone density, its safety and the likelihood that people will stick with it.

For instance, other studies have shown that jogging helps maintain bone density. But its high-impact nature carries greater risk of injury, particularly for older women. In addition, 50-year-old women who have never jogged are unlikely to adhere to a jogging routine for any length of time.

But Turner considers yard work an ideal activity that matches all three health concerns. "The best thing about yard work is that so many people are willing to do it. They don’t dread it as exercise," she said. "People have other motivations for gardening. They take pride in a beautiful yard and pleasure in being outdoors. They’ll probably continue to do it as long as they’re able."

And as long as people stick with an exercise, they can harvest the benefits well into old age. Turner adds a cautionary note, however. Digging into a garden does not guarantee that everything will come up roses for those at risk for osteoporosis, she says.

In addition to exercise, women must take other precautions, and they must take them as early in life as possible. Turner recommends that all women take in at least 1,000 milligrams of calcium a day, that they maintain a healthy body weight, and that they refrain from smoking or excessive alcohol consumption.

"There are a lot of factors that contribute to osteoporosis," Turner said. "But the more we know, the more we can encourage women to maintain healthy lifestyles and the more power we can give them to prevent this disease."